Not applicable.
Not Applicable.
Not Applicable.
1. Field of the Invention
This invention relates to a radio-controlled model car engine cooling system using both air-cooling and water-cooling of the engine cylinder head.
2. Description of Related Art
Internal combustion engines are commonly used to power model airplanes, boats, and cars. Model boats and cars also may use battery-powered electric motors, however the internal combustion engine provides higher performance. These model vehicles usually feature remote radio control of the vehicle speed, steering, and in the case of airplanes, the vehicle altitude. The operator uses controls connected to a radio transmitter to transmit signals to a radio receiver on the vehicle that will position the throttle of the engine and control the vehicle steering mechanism using servomotors. The performance of the vehicle depends on many factors, one being the choice of engine design, of which many are available, the size of the engine, which is often limited by the size of the vehicle, and the engine performance characteristics.
Various engine designs are available, including 2 and 4 stroke models, gasoline or nitro-methanol fueled. The 2-cycle nitro-methanol fueled engine is popular due to advantages in the initial cost, the performance for a given space requirement, weight, and the availability of parts and supplies. A typical nitro-methanol 2-cycle engine is a single-cylinder design. Lubrication is by mixing lubricating oil in the fuel, and this fuel-oil mixture is routed through the crankcase prior to entry to the cylinder. The engine has no valves as the fuel-air mixture entry to the cylinder and the exhaust from the cylinder is through ports that are uncovered by the piston near the bottom of the engine stroke. Ignition is by a glow plug, a hot wire in the top of the cylinder. The glow plug is initially electrically heated to start the engine and then retains sufficient temperature for ignition from the heat of combustion. The performance of an engine may vary with the condition of the engine; the fuel-air ratio provided by the fuel control, which is typically a needle valve in the fuel passage to the engine air intake; and the composition of the fuel.
Fuel for the 2-cycle engine is a mixture of methanol; nitro methane, commonly called nitro; and lubricating oil, typically castor oil or synthetic oil. This mixture is often called nitro-methanol. The proportions of the fuel mixture can be varied to obtain the desired engine performance. A variety of fuel component proportions are available pre-mixed or the operator may mix the components. In a given engine, higher performance can generally be obtained by increasing the proportion of nitro methane in the mixture. There is, however, a practical limitation to the nitro methane content that can be effective in boosting performance in a given engine. This limitation is based on the need to provide sufficient lubrication of the engine, compression ratio limitations on the effective use of increased nitro methane content, fuel-air ratio capability of the fuel metering control, and the cooling available to the engine. Increasing the nitro methane content of the fuel will increase engine temperature therefore increasing the need for engine cooling.
Engine cooling for 2-cycle internal combustion nitro-methanol fueled engines varies by the type of vehicle in which the engine is installed. Airplanes generally have good airflow to the engine and small cooling surfaces on the exterior of the engine cylinder and cylinder head provide sufficient cooling. Boat applications typically have the engine enclosed in the boat hull where airflow is minimal, so liquid cooling is provided to the cylinder head which contains water passages. The water passages are provided cooling water flow using the water in which the boat floats. Model cars typically have the engine enclosed by the car body, however provision is made to provide restricted airflow to the engine. An extensive stack of cooling surfaces is provided on the cylinder head for air-cooling. The engine in a model car necessarily has restricted airflow to the head cooling surfaces due to the need to fit around the engine the gear-reduction transmission, engine starting mechanism, steering mechanism, radio receiver and servos, radio battery, and fuel tank. All these components are contained on the chassis beneath the car body. In order to provide a realistic looking model car, the car bodies typically cover the entire chassis. The combination of airflow restrictions surrounding the engine and enclosure in the car body leads to operating problems including loss of power due to overheating.
Experience with operation of nitro-methanol fueled model cars has shown problems that are related to the engine cooling. Operation of these cars in high temperature locations provides erratic performance due to the limited cooling available to the engine causing extreme a engine temperatures. Extreme temperatures shorten the life of engine components, as proper lubrication is more difficult to establish and maintain. Car bodies are generally made of a thin plastic material. In the vicinity of the engine, the plastic is subject to discoloration and deformation from the engine heat. Often the car operator will cut a hole in the car body in the vicinity of the engine to remove or prevent damage and to attempt to improve engine cooling. The resulting model car body is unrealistic looking due to the unsightly hole showing the top of the cylinder head. High engine temperatures also make burn injuries likely when the operator is making engine adjustments.
A model car operator desirous of increasing the performance of a given car does not generally have the option of installing a larger size engine. This is due to the space limitations of the car chassis. The options for engine performance improvement are limited to improving the performance of an engine of the present size. Increases in performance can be made by modifying the engine to increase engine displacement by replacing the cylinder liner, piston and piston rod. Such a replacement is usually also accompanied by a change in fuel composition as the modified parts are generally designed to optimize engine performance at a higher nitro methane fuel content. Simply increasing the fuel nitro methane content also can make a limited performance improvement. Unfortunately these performance improvements increase the heat developed by the engine, resulting in exacerbation of the problems described above of high engine temperature.
There is a need among operators of 2-cycle nitro-methanol fueled engine model cars for a way to improve performance without exacerbating the problems the cars have due to poor engine cooling.
One object of the present invention is to provide a model car engine cooling system that will supplement the engine air-cooling to provide stable performance in warm temperatures.
A second object of the present invention is to provide a model car engine cooling system that maximizes engine cooling for a given model car chassis and body layout.
A third object of the present invention is to provide a model car engine cooling system that provides supplemental cooling without the need to make substantial modifications to the car body.